The RBX-GT2 is the engine spec in the 400R and Z-tune: It's an RB26 built around an N1 block and ancilleries, but features a 77.7mm stroke crank and forged pistons, plus special head prep work and more agro cam specs than yer boggo RB26. Comes out to 2.8L (or 2770cc, as ppl have mentioned. same as the old HKS stroker crank).
I doubt you'd find a genuine one anywhere outside of the car it came in, even a dead one.